Talk:Seibel S-4/Example

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The Seibel S-4 was the second helicopter designed and built by Seibel Helicopter Company's Charles Seibel. The S-4 was evaluated by the United States Army under the designation YH-24 Sky Hawk but would be rejected for service. The S-4B would serve as the basis for the design of the Cessna CH-1 Skyhoook, the only helicopter Cessna ever produced.

S-4

S-4 in Flight as the YH-24

Type Helicopter
Manufacturer Seibel Helicopter Company
Designed by Charles Seibel
Maiden flight 1951
Primary user United States Army
Number built 2

Contents

[edit] Development

Charles Seibel began development on the S-4 after forming the Seibel Helicopter Company with funding from local Kansas oil investors. The S-4 was a continuation of his work on his previous design, the Seibel S-3, which he flew as a demonstrator for his design concepts; primarily a new design for a two-bladed rotor system and a simplified transmission. These features would also be incorporated into the S-4 design.

In January 1949, the S-4 lifted off the ground for the first time, piloted by Johnny Gibbs. In March 1950, certification tests where completed and on 23 April 1950, the S-4 received civil certification by the CAA. A larger engine, the Lycoming O-290B with 125 hp, would be installed in the aircraft, making it the S-4A.

[edit] Design

Gov. Frank Carlson and Charles Seibel at the CAA Certification Ceremony
Gov. Frank Carlson and Charles Seibel at the CAA Certification Ceremony

The S-4 frame was a welded steel-tube box frame, with two decks. A lower deck supported the control panel, pilot's seat, wheeled, tricyle landing gear, and a small passenger/cargo area accessible from the rear, and an upper deck carried the engine, the fuel and oil tanks, and supported the transmission and rotor assembly. A tapered, monocoque, alloy tail boom with a two-bladed antitorque tail rotor was attached at the rear of the upper deck.

[edit] Operational history

Both the United States Army and the United States Air Force showed interest in the S-4. In the beginning 1951, the Army, ordered two helicopters for evaluation as a possible replacement for the OH-13 in the observation, utility, and aeromedical evacuation roles. The Army designated the S-4 as the YH-24 Sky Hawk. The first Sky Hawk, serial number 51-5112, was delivered to Fort Bragg, North Carolina in April 1951; the second YH-24, serial number 51-5113, was delivered to Wright Field. Based on feedback from the Army during the evaluation, Seibel, shortened the fuselage of the second YH-24 (51-5113) and widened the cockpit for a co-pilot's seat next to the pilots seat. Seibel also replaced that aircraft's original wheeled, tricyle undercarriage with landing skids. This aircraft would become the S-4B. Despite the simplicity of the S-4, the Army determined that it did not provide a sufficient payload capability and the aircraft were dropped from the inventory and returned back to Seibel in 1952.

[edit] Variants

S-4 
Original design, certified by the CAA in 1950.
S-4A 
featured an upgraded, 125 hp Lycoming O-290B engine.
S-4B 
Modified airframe based on Army recommendations during YH-24 evaluation. Two-seat cockpit and skid landing gear.

[edit] Specifications (YH-24)

Orthographic projection of the Seibel S-4.

General characteristics

  • Crew: 1-2
  • Capacity: 583 lbs (265 kg)
  • Length: 27 ft 10 in (8.48 m)
  • Rotor diameter: ()
  • Height: 10 ft 1 in (3.05 m)
  • Empty weight: 946 lb (430 kg)
  • Max takeoff weight: 1529 lb (695 kg)
  • Powerplant: 1× , 125 hp (95 kw)

Performance


[edit] References

[edit] See also

Related development

Comparable aircraft

Related lists